FUNCTION: The obscurin gene spans more than 150 kb, contains over 80 exons and encodes a protein of approximately 800 kDa. The encoded protein contains 68 Ig domains, 2 fibronectin domains, 1 calcium/calmodulin-binding domain, 1 RhoGEF domain with an associated PH domain, and 2 serine-threonine kinase domains. This protein is one of three giant sacromeric signaling proteins that includes titin and nebulin. It may have a role in the organization of myofibrils during assembly and also may mediate interactions between the sarcoplasmic reticulum and myofibrils. Alternatively spliced transcript variants encoding different isoforms have been described although the full-length nature is not known for all splicing variants. [provided by RefSeq, Jan 2010] PHENOTYPE: Mice homozygous for a knock-out allele exhibit centrally localized nuclei in muscle fibers and mild myopathy in aged mice. [provided by MGI curators]